A storage system that is configured by a plurality of physical storage devices (such as an HDD (Hard Disk Drive) and a flash memory device) is known publicly. As a storage system, there can be known publicly for instance a system that is provided with a cache memory that stores data that can be read and written in addition to a simple read and write function, a redundant controller system, and a system that is provided with a snapshot function that carries out a duplication of a volume in little time.
Such a storage system is provided with a wide variety of functions as described above. In recent years, such a storage system has been provided with a memory with a large capacity, a DRAM (Dynamic Random Access Memory) in a quintessential way in order to implement a cache memory. The DRAM stores data that is used for a host computer (data that is read or written by a host computer, hereafter referred to as a user data) and data that is used inside a storage system to implement a wide variety of functions (hereafter referred to as a control data).
On the other hand, it is publicly known that an error occurs for a DRAM. The error is that a minimum access unit to one chip is increased, the number of chips that can be read or written at one time is decreased, and incorrect data is stored for instance. The technique for adding an error correcting code (ECC) and enabling a data error correction and a detection in the case in which an error occurs is publicly known (see Patent Literature 1).
Moreover, a method for carrying out an appropriate control in the case in which a DRAM error occurs and for maintaining the availability and a reliability of a storage system has been disclosed. For instance, Patent Literature 2 discloses a processing method of a storage system in the case in which a DRAM error occurs.